Such a switching device is known from EP2 061 053 A2. For creating a switching device for direct current applications it is recommended that the housing of a switching device for alternating current applications be used, whereby additionally a magnet is provided, which is creates a magnetic field with field lines predominantly transverse to the isolation gaps of current paths of the alternating current switching device. In the housing there are three receiving regions for each single current path, whereby each current path is assigned a moveable switching contact element as well as two fixed switching contact elements opposite each other. The three moveable switching contact elements can be moved together, between a closed position which corresponds to the switched-on status of the switching device, and an open position which corresponds to a switched-off status of the switching device. The individual current paths are each assigned two arc extinguishing devices in the form of extinguishing plates, arranged individually over one another and electrically insulated from each other. In addition, each current path has two separation sections which, when the movable switching contact elements are open, form between the ends of the movable switching elements and the first and second fixed switching element which are associated with the ends of the movable switching contact elements. On opening of the switching contact elements an arc, which can be extinguished with the help of an arc extinguishing devices, is formed along each separation section. Since arcs in direct current applications cannot be extinguished during zero current passing as in alternating current applications, a magnetic field that drives the arc into an arc extinguishing device has to be used in direct current applications. This magnetic field is built up by permanent magnets, whereby a magnetic field is built up with field lines in a direction which runs transverse to the separation sections and creates a Lorenz force on the arcs that form along these separation sections which drives an arc in the direction of an arc extinguishing device. In this connection, an arc between a first contact pair is driven in the direction of a first arc extinguishing device and the arc between a second contact pair is driven in the direction of the second arc extinguishing device. Since the movement of the arcs is dependent on the direction of the current, the switching device is suitable only for one current direction, i.e. poling. If the switching device is operated in the opposite current direction, the arcs will not be driven into the arc extinguishing devices but in the opposite direction onto a switching bridge. Even if the magnetic poling of one of the arcs is reversed, one of the arcs would run towards a switching bridge, which would result in reduced lifetime, since the switching bridge or other part would be damaged or even destroyed in the long-run.
The EP 0 789 372 B1 also shows a switching device of the type mentioned at the outset. A fixed contact is provided with a fixed arc runner which is circular-arc-shaped. A moveable arc runner is provided on a moveable contact, whereby an arc can form between the two arc runners which can be moved in different directions by the arc driver assembly in accordance with the direction of the current. In accordance with the direction of current this is diverted around a centre point, either in the first direction of rotation or in a second direction of rotation opposite to the first, whereby the centre point corresponds to the centre point of the fixed arc runner. An arc with the first direction of current is diverted into a first arc runner channel and an arc with a direction of current opposite to the first direction of current is diverted into the second arc runner channel. Both arc runner channels run around the centre point and are arranged next to each other separated by an insulating wall. The arc runner channels are part of an extinguishing device for extinguishing of the arc Further, the extinguishing devices comprise extinguishing plates which are radically oriented to the stationary arc channels. The extinguishing plates are arranged in such a way that they cover both the arc channels and therefore are part of both extinguishing devices.
An aspect of this invention is to provide a switching device that can be operated independent of polarity and one that is constructed in a simple manner.